During the Twin Peaks panel at San Diego Comic-Con, a fan asked the cast members of the revival how much they ad-lib on set. Show creator David Lynch, the man behind Blue Velvet and Eraserhead, has a very specific style and vision, so it’s hard to imagine that he would be open to changing the script on the fly. And indeed it turns out Lynch isn't exactly flexible when it comes to his show.
To answer the question, star Kyle MacLachlan decided to share an anecdote about a legendary actor who tried to improvise on the Twin Peaks set.
“I can tell a brief story about an actor who’s not here named Jim Belushi,” he said. “Jim decided he was going to ad-lib a line in this heightened moment of euphoria, which he did. And we heard, ‘Cut!’ And David has this megaphone, and he said Mr. Belushi, ‘Do I have to report you to the principal's office?’ And Jim said, ‘No, sir. Got it.’ I hope that helps answer your question."